Fluid cooled tube



y 1937- I R. H. VARIAN I 2,079,137

FLUID COOLED TUBE Filed March 13, 1935 INVENTOR.

RUSSELL h. VAR/AN.

ATTORNEYS.

Patented May 4, 1937 FLUID COOLED TUBE Russell H. Varian, San Francisco,Calif., assignor to Farnsworth Television Incorporated, a cornotation ofCalifornia Application March 13, 1935, Serial No. 10,887

1 Claim.

My invention relates to the construction and apparatus for the coolingof thermionic tubes.

Among the objects of my invention are: to provide a simple and improvedconstruction for fluid cooled tubes; to provide a tube wherein tubularmetal to glass seals in the construction of the envelope therefore areavoided; to avoid degassing diillculties inherent in fluid cooled tubesof the type in which one of the electrodes forms part of 10 the tubeenvelope; to provide a fluid cooled tube, capable of handling highpower, which compares, in size and manufacturing cost, with air cooledtubes of lesser capacity; to provide a fluid cooled tube wherein theelectrode carrying high potential. may be insulated from the coolingmeans; and to provide an improved anode construction for fluid cooledtubes.

Other objects of my invention will be apparent or will be specificallypointed out in the descrip tion forming a part of this specification,but I do not limit myself to the embodiment of the invention hereindescribed, as various forms may be adopted within the scope of theclaim.

Referring to the drawing:

The flgure is a vertical sectional view of a thermionic device embodyingmy invention.

Broadly, my invention comprises a space discharge tube, or otherthermionic device, having a vitreous envelope with an electrode formedon an area of the inner surface thereof, by the deposition of aconductive film, which is in atomic contact with the envelope. Means areprovided, circumiacent the envelope and overlying and preferablyinsulated from the area covered by the con- 35 ductive fllm, forpermitting the dissipation of heat from the film.

In thermionic tubes capable of handling high power, in the order of oneor two k. w., considerable heat is generated, in the tube, due to the 40heavy electronic bombardment of the anode. It is necessary, in order toprevent damage to the tube, to dissipate this heat; this usually beingdone by forming the anode as a cylindrical part of the tube envelope andproviding a jacket thereabout,

5 through which water, or other cooling fluids, may be circulated. Dueto its high heat conductivity, copper is generally used for the anodematerial.

Several difficulties arise in the construction and use of tubes of thistype, one of these being the 50 diillculty in obtaining, andmaintaining,a proper seal between the metal and glass parts of the envelope due tothe wide difference in the rates of expansionand contraction of the twomaterials.

Another difllculty experienced is in the evacuu ation of the tube. Inorder to drive occluded gases from the copper anode, the temperature ofthis electrode must be raised to a high degree, causing expansion in themetal, which, if it does not rupture the seal, will cause minute crackstherein. leakage of air, into the envelope, to destroy the usefulness ofthe device.

In the use of these tubes, another undesirable feature presents itself,in that, to prevent serious radio frequency losses, or current leakagedue to the difference in potential between the anode and the watersupply, which is usually at ground potential, banks of coiled watercirculating conduit are interposed in the inlet and outlet leads to thewater jacket to provide a high resistance path from the anode to thewater source, or ground.

I have provided an improved means for cooling the tube whereby the sizeand space required for the resistance coils, mentioned above, may bereduced.

In greater detail, the structure of my invention comprises an evacuatedvitreous envelope 2 having a cathode 3 and a control element or grid 4mounted therein. The envelope is provided, at its upper end, with anextension 6 into which a lead 1, terminating in a button 8, is sealed. I

An anode 9 is provided, and comprises a metallic fllm deposited on theinner surface of the envelope. This film may be produced by one ofseveral methods, such as the method employed so in silvering mirrors, orby the process of evaporation of metals in vacuo.

I prefer, however, to produce the metallic film by depositing a thinlayer of platinum, by the use of a platinizing solution, on the interiorsurface of the envelope, and burning this layer into the vitreousmaterial so that it is actually in atomic contact therewith. Successivelayers of metal may then be deposited on the base layer to build up thefilm to the desired thickness. As a result, the finished anode is weldedto the envelope, and of course, to the button 8.

Means are provided circumjacent the envelope, and overlying the areacovered by the metallic film anode, for permittingdissipation of heat *5from this electrode. A housing ii is provided, having end walls I! andI3, in which apertures l4 and it are formed. These apertures,respectively, are slightly larger than the extension 6 and the lowerportion of the envelope, so that so resilient gaskets i1 and I! may beplaced therein to provide water tight connections between the jacket andthe projecting portions of the envelope. An inletpassage l9 and adischarge passage ll are provided, communicating with the I These, intime, will allow suflicient 5 7 interior of the water jacket, to whichsuitable conduits may be attached to permit circulation of cooling waterfrom an external source, such as the building mains, through the housingll 5 to cool the tube.

Due to the large capacity between the insulated anode and thesurrounding water, the use of cooling water direct from any source atground potential is not practical when the tube is used 10 at radiofrequencies. Consequently, it is advisable to provide the usual banks ofwater conduit, such as used in connection with the tubes describedabove, wherein the anode is formed as part of the envelope. However, dueto the insu- 15 lation ailforded the anode by the envelope, these coils,for use with the present tube, need not be as large as those used withthe previously described tube. It has been found, also, that in certaininstances, where the tube is used for low 30 frequency work, that thecapacity between the anode and the water will not seriously affect theoperation of the tube when the cooling water is taken direct from thesupply mains.

I may prefer to use a dielectric fluid as the s cooling medium, in whichevent it is obvious that, due to the anode being insulated from thefluid, a further reduction in the size, and consequently the spacerequired for the resistance coils, may be eflected.

The tube just described is far superior to the water cooled tubes inpresent use, in that all tubular seals between vitreous and metal parts,in the envelope construction, are avoided; the rates of expansion of theenvelope and the me- I tallic illm anode are so nearly alike thatrupture of the envelope, due to uneven expansion of these two parts, isimprobable; and the insulated feature of the anode greatly simplifiesthe construction of the cooling water system and allows it to m bematerially compacted. The cooling eiliciency is good, and higher powerscan be handled than with any air cooling systems.

I claim: 15

A fluid cooled electrical discharge device, comprising an insulating,heat conducting envelope. an electrode disposed within said envelope inatomic contact with the interior surface thereof and a cathode, ahousing for liquid disposed about on said envelope to enclose the areacovered by said electrode, a lead wire from said electrode passingthrough the space enclosed by said housing, and means forming anextension of said envelope for insulating said lead wire from contactwith 26 the liquid in said housing.

RUSSELL H. VAR-IAN.

